For some, the real lesson of robotic exploration might be that we should not send people at all. If NASA’s only goal was scientific discovery, robotic probes would certainly be cheaper and lower risk. Yet NASA is tasked with more than just science; science is only one aspect of a broader human impulse to explore. Space exploration has wide appeal because of a desire for ordinary people to experience it firsthand someday. Robotic probes are just the first wave of solar system exploration. Government-funded human missions will be the second wave, and the third will be private citizens seeking their fortune and adventure in space. NASA’s past investments developed the technology that is fueling today’s commercial space race, with capsules launching to the space station and space planes jetting over the Mojave Desert [see “Blastoffs on a Budget,” by Joan C. Horvath; Scientific American, April 2004]. NASA can now develop the technology that we will need to push deeper into the beyond.
Flexibility Is the Watchword
Three basic principles govern the course we recommend. The first is the “flexible path” approach that the Augustine commission advocated and that President Obama and Congress accepted. This strategy replaces the old insistence on a fixed path from Earth to moon to Mars with an extensive selection of possible destinations. We would begin with nearby ones, such as the Lagrangian points (locations in space where an object’s motion is balanced by gravitational forces) and near-Earth asteroids.
The flexible path calls for new vehicle technologies, notably electric propulsion. We propose using Hall effect thrusters (a type of ion drive) powered by solar panels. A similar system propelled the Dawn spacecraft to the giant asteroid Vesta and will, by 2015, carry it onward to the dwarf planet Ceres [see “New Dawn for Electric Rockets,” by Edgar Y. Choueiri; Scientific American, February 2009]. Whereas traditional chemical rockets produce a powerful but brief blast of gas, electric engines fire a gentle but steady stream of particles. Electric power makes the engines more efficient, so they use less fuel. (Think space Prius.) Because the price of this greater efficiency is lower thrust, some missions can take longer. A common misperception is that electric propulsion is too slow for crewed spaceflight, but there are ways around that. The idea that emerged at our first brainstorming session was to use robotic electric propulsion tugs to place chemical boosters at key points in a trajectory like a trail of bread crumbs; once the trail is laid, astronauts can set out and pick up the boosters as they go along. In this way, missions get the fuel efficiency of electric propulsion while keeping the speed advantage of chemical propulsion.
Crucially, electric propulsion saves money. Because the ship does not need to lug around as much propellant, its total launch mass drops by 40 to 60 percent. To first order, the price tag of space missions scales linearly with the launch mass. Thus, slimming the mass by half could cut the cost by a similar fraction.
Many space enthusiasts wonder why we would bother visiting an asteroid when Mars is everyone’s favorite destination. Actually asteroids are the perfect targets for an incremental approach toward reaching Mars. Thousands are sprinkled through the gap between Earth and Mars, providing literal stepping-stones into deep space. Because asteroids’ gravity is so weak, landing on one takes less energy than reaching the surface of the moon or Mars. It is hard enough to mount a long interplanetary expedition—six to 18 months—without also having to develop elaborate vehicles to touch down and blast off again. Asteroid missions let us focus on what, in our estimation, is the most complex (and still unsolved) problem for humans ever to venture far from Earth: learning how to protect astronauts from the deleterious effects of zero gravity and space radiation [see “Shielding Space Travelers,” by Eugene N. Parker; Scientific American, March 2006]. As NASA gains experience dealing with the hazards of deep space, it will be in a better position to design vehicles for Mars surface missions.
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28 Comments
Add CommentWHat is with Sciam and its incredibly stupid aversion to nuclear power. Is it completely in Big Oil's pocket?
Reply | Report Abuse | Link to thisIf you rewrite this entire article using nuclear powered space craft as the Chinese certainly will the entire solar plan outlined here becomes nonsense.
Here's part of the Chinese plan.
They drill a hole in a salt formation. Put a small nuke at the bottom in a water tank, put a thick steel plate on top of the tank with a automated payload capsule on top. Light the nuke and let er rip.
3000 tons at $10 a lb straight to the moon. I'm sure the Chinese are drilling while we twiddle our thumbs.
Seal the hole and drill a new one for the next load.
www.nextbigfuture.com/2010/03/150-kiloton-nuclear-verne-gun.html
They will launch a few nuclear engines from stolen updated NASA Nerva designs and be flitting around the Solar system in no time.
I got an idea, Despite being in the depths of worldwide near-depression, get all the countries to pool 10& of their money for the next 30 years and place a permanent colony of a dozen human beings on Mars. Makes perfect sense.
Reply | Report Abuse | Link to thisYour idea still doesn't get people to Earth orbit as the g-forces would be extreme. The g-loading also requires that your payload be incredibly secure, and the vessel incredibly strong.
Reply | Report Abuse | Link to thisAs a side note, I think you'll be interested in this article:
http://www.guardian.co.uk/environment/2011/jun/23/thorium-nuclear-uranium
I had only heard the positives of thorium energy up until I read this, but I always knew there was a catch. It might still pan out, but we need to get a research reactor up and running with all the money we're throwing away on conventional nuclear reactors.
Does anybody know what the effectiveness of using water (H2O) as a radiation shield? Do you only need a couple of centimeters mean thickness in a water shield to bring interplanetary radiation under a reasonable level, or is it more like meters? If you need several meters of water surrounding the crew capsule, just like what is required in the nuclear power industry, then we may have to use those near-Earth asteroids as our spacecraft of choice. Drilling into 100m+ size asteroids would give astronauts all the protection they would need and their whole spacecraft could be an object of study as they venture to other destinations. Changing a 100m asteroid's orbit might be complicated, however.
Reply | Report Abuse | Link to thisWe already have fairly easy access to space for the manned crews required. And more is coming very soon - dirt cheap from SpaceX
Reply | Report Abuse | Link to thisWhat we lack is the ability to get vast amounts of cargo up there dirt cheap allowing significant industrial facilities to build up to the point where eventually lunar and asteroid water, carbon and mineral resources become available.
The Guardian article is just the usual low information and thoroughly debunked nonsense from the Big Oil funded anti nuclear lobby. The article starts off with the enormous lie and just keeps it up.
"...like all nuclear power production they rely on extensive taxpayer subsidies..."
There are no nuclear subsidies of any sort today and past ones are a canard based on fantastic allocations of military research on ship power plants and weapons. In fact today the US nuke industry is $80B in the black with never to be used funds held by the DOE.
Flibe energy staffed by some of the US's leading nuke engineers is at work putting their money (no subsidy) where their mouth is building a MSR SMR sized for the US military - service in 5 years.
This is the report that the article was based on:
Reply | Report Abuse | Link to thishttp://ripassetseu.s3.amazonaws.com/www.nnl.co.uk/_files/documents/aug_11/NNL__1314092891_Thorium_Cycle_Position_Paper.pdf
It seems like this technology won't be as easy as you imagine. There are many reasonable points brought up and as a thorium power advocate, I thought you could address them. If Flibe can get a research reactor up and running in 5 years, that would be interesting. Maybe the high power to mass ratio of these reactors could power the ion engines on the spacecraft envisioned in this article, but getting the reactor up and running would be a good first step.
However, if the Price Anderson Act, or the Nuclear Loan Guarantee aren't subsidies, then renewable energy should have ALL of its insurance covered by the government too so that the energy market isn't distorted.
New nuclear gets the same production tax credit as wind power:
http://www.sseb.org/wp-content/uploads/2010/05/SCANA-2011-Nuclear-PTC-Allocation-for-public-private-partnerships-Jan-2011.pdf
In addition, many of the technologies developed in the Manhattan Project went straight into LWR design and the Uranium Fuel Cycle was chosen PRECISELY because it was the most mature fuel cycle at the time (1950s) due to the nuclear weapons program.
Here's a solid report of the history of energy subsidies from the U.S. Government:
http://www.dblinvestors.com/documents/What-Would-Jefferson-Do-Final-Version.pdf
Regardless of the energy source, there never has been a Free Market in energy and EVERY energy source has been the benefactor of government funds in some form and magnitude.
Man, the SciAm spambot blocker keeps dinging me because I bring too many references to the discussion. I guess I just have to keep typing to get past it. Sorry everybody has to read this...
"Regardless of the energy source, there never has been a Free Market in energy and EVERY energy source has been the benefactor of government funds in some form and magnitude."
Reply | Report Abuse | Link to thisSo... why should we care if thorium LFTR R&D is government subsidized? IMO it seems like good thing for government funding to be shifted that direction.
Also, the point made in that Guardian article, that building a thorium reactor still produces the same nuclear waste and is still ultimately adding to the total global production of nuclear waste. While that point may be true, they fail to take into consideration the number of uranium reactors that are currently in the works which produce MORE nuclear waste per Kw hour of electricity, and whose fuel is more rare and takes much more energy to refine to a useful state. All of these things cost the taxpayer money in the form of nuclear subsidies, money which I believe would be better spent researching and testing what COULD be a better and more efficient reactor design.
I was disproving seth's comment:
Reply | Report Abuse | Link to this"There are no nuclear subsidies of any sort today and past ones are a canard based on fantastic allocations of military research on ship power plants and weapons."
Yeah, I would much rather have the subsidies and loan guarantees that are going towards LWRs be directed towards LFTR research / building a test reactor. However, the thorium boosters posit this technology as having no downside and I was just wondering what seth's response is to the issues brought up in the NNL report.
Nasa will come up with an expensive nonsense type solution. It will not be used of course but "studied".
Reply | Report Abuse | Link to thisThe Technology used by the Flying Saucer, discovered, patented and explained to the low IQ brains of Nasa, seems not to get through. Please hire some teen-agers instead of Rocket Propulsion Experts.
Honestly. Our Rovers are intruders into the Mars (and Venus) communities already. So are our bombs, to the Moon; our spent nuclear engines on Jupiter. ... We have no natural right to intrude on other peoples' planets.
Reply | Report Abuse | Link to thisuhhhh, Emily..."other people's planets." You are obviously plugged in somewhere the rest of us aren't.
Reply | Report Abuse | Link to thisCS (chuckling softly)
Er, for what purpose? Hitting golf balls around, maybe?
Reply | Report Abuse | Link to this"All the countries?" I nominate you to be in charge of collecting donations, but don't call me. I'm not willing to spend a penny to put humans in space, anywhere any time. Robotic science, yes.
Grumpy - You beat me to it. Emily seems to be a prime example of our public school alumni. Lots of fluff, no substance.
Reply | Report Abuse | Link to thisGrumpy, I've been re-rendering NASA photos for the past five years. They DELIBERATELY AVOID Life. It is NOT TO BE ALLOWED to show. I have Facebook Albums, Google ALBUMS that display Martian, Lunar and other Sphere LIFE that NASA/NSA/NRO all deny. Life is multi-dimensional, Life is everywhere. Our leaders operate from ignorance.
Reply | Report Abuse | Link to thishttps://picasaweb.google.com/110893507785869610783/THEPEOPLEOFMARSINPICTURES
https://picasaweb.google.com/110893507785869610783/GOOGLEMOONNASARERENDERED
https://picasaweb.google.com/110893507785869610783/MOONVIDEOSRERENDERED
What can I say? Scientistic dogmatists PREFER something else. :shrug:
Regarding sethdayal's comment "There are no nuclear subsidies of any sort today": Unfortunately this statement is factually inaccurate, as sault notes. The The Nuclear Waste Policy Act of 1982 charges nuclear power generation companies 1/10 of a cent per kilowatt-hour generated (i.e. about 1% of the retail cost of electricity of $0.10/kwh) to handle all nuclear waste issues. These funds go to the federal government, which is in turn responsible for accepting all radioactive waste from those companies for longterm storage, *regardless* of the cost that storage might entail. Without reprocessing (which I favor), currently blocked because of (probably spurious) nonproliferation concerns, longterm safe storage may prove either impossible or grossly more expensive; we just don't know. Note the failure of Yucca Mountain. This was provided in order to provide a stable funding environment for the nuclear power companies. Sure looks like a (possibly really big) subsidy to me. Better - IMHO - that we should do research on ways to reprocess and "burn up" such used radioactive fuel rods - planning for storing *anything* on a 10,000 or million year timeframe is ludicrous, much less anything so toxic; that would be a terrible legacy for our n-grandchildren.
Reply | Report Abuse | Link to thisNow, onto the "This Way to Mars" article itself. There is another advantage of putting astronauts into Mars orbit, probably on Phobos or Deimos, for a multiple-month stay. In addition to studies on the moon itself, they could also provide piloting for remotely-operated vehicles on the Martian surface on a near-realtime basis. Mars rovers currently move and conduct science VERY slowly because of the 15-to-80 minute (one-way) lightspeed delay; they must be given a lot of Artificial Intelligence, and in practice can be commanded from Earth usually only once per 24 or so hours. Whereas an astronaut on a Martian moon could "drive" a rover with a time delay of only 1 or a few seconds, covering much more territory and conducting science much more rapidly. It goes without saying that such an astronaut would need to be FIRST a highly trained scientist/geologist (areologist?), and only secondarily an astronaut/engineer, not the other way around. (Take THAT, NASA!).
Reply | Report Abuse | Link to thisEmilyCragg: I looked at your 're-rendered NASA photos' and all you have done is make little rectangles and circles around various rock formations and you then magically call these rock formations 'people'. I think you have been smoking WAY too much Sour Diesel ganja. Is a pile of rocks a person in your world ?
Reply | Report Abuse | Link to thisA bit more than five pages of article, and nowhere any mention of cooperation with other countries in the endeavour, which will indubitably prove daunting, to get human space exploration beyond the moon ! Whether such exploration is really the path to go is a matter open to question, but what is not, in my opinion, is the fact that no country will prove able to bear its costs alone. If the United States government is indeed serious about this matter, it is going to have to embrace cooperation with all comers - including not merely the Russians ESA, and JAXA, but also and not least the Chinese (pace Frank Rudolph Wolf) - otherwise humanity is unlikely to overcome the limitations that gravity wells and interplanetary radiation, etc, place upon it....
Reply | Report Abuse | Link to thisHenri
Oops, recalculation, oneway lightspeed time from Earth to Mars is about 5-20 minutes depending on orbital positions (not 15 to 80) - my bad, sorry.
Reply | Report Abuse | Link to thisNASA might as well dream of Mars! They have no where else to go!
Reply | Report Abuse | Link to thisLERO -- Low Earth Ruble Orbit -- is out of their reach.
Bureaucrats.
sault, I recall reading that more than a few cm will be needed for protection against cosmic rays on long duration missions.
Reply | Report Abuse | Link to thisSome obvious techniques to reduce the mass of shielding suggest themselves:
- Heavily shield a smaller volume where crew sleep and work much of the time, while shielding other areas less
- Combining magnetic shielding with mass.
You don't need to actually burrow into an asteroid to get the benefit of shielding by mass. Just being against or close to a mass of rock will block some of the radiation. The region between the heavily shielded 'storm shelter' and the asteroid becomes a much safer zone. Gather some regolith from an asteroid into bags for extra shielding at the sides.
There is an interesting discussion of radiation from a hard science fiction perspective here: http://www.projectrho.com/rocket/radiation.php
@sault Our March 2006 issue has an article on the radiation question. You'd need 5m water depth. Sorry about the spam filter, by the way - we editors have no control over it or, for that matter, over any of the site design...
Reply | Report Abuse | Link to this@sethdayal Huh? Why do you jump to the conclusion that the Sci Am editors have some general aversion to nuclear power. We don't - quite the contrary. Even if we did, we wouldn't insist that all our authors toe the line.... This article concerns inner-planet missions for which solar is the more economical choice. Outer-planet missions would be a different matter.
Reply | Report Abuse | Link to this"The authors argue that engineers need to assume that the political process will continue to be unpredictable—and plan for it. They must design mission options that can be ramped up or down as circumstances change."
Reply | Report Abuse | Link to thisUnfortunately this is false. The political process where NASA HSF is concerned is very predictable. Projects which maximize the number of jobs in key districts are rewarded with multi-billion dollar sole-source contracts, even when project failure is nearly certain. Those which show real promise of expanding our capabilities and lowering costs are "too risky" and "too expensive in a time of fiscal belt-tightening".
I'm sorry, but I don't see something like this happening without either a significant increase in NASA's budget fueled by an improbable surge in public support, or a coordinated and persistent effort by advocates to pull the leeches off the space program.
In all this wonderful planning, projection, and forecasting, there is just one tiny shred of actual justification for the entire effort, and it amounts to nothing but an appeal to human curiosity and desire for adventure.
Reply | Report Abuse | Link to thisSatisfying human curiosity does not require spending taxpayer's money on manned space flight, since it can be satisfied, and is being satisfied, by unmanned space exploration. Satisfying the human desire for adventure should not be a goal of government expenditure at all. If people want to have adventures in space, let them fund it for themselves. We have far more pressing matters for government to address here on earth--matters that affect the lives of millions. People who never outgrew Buck Rogers or Captain Kirk should either find ways to mature, or pay for their own wish-fulfillments.
What about the space elevator? Made out of carbon nano tubes. To get the pay load in orbit. space-x to get the men required in orbit. Space station for housing. Bring back the shuttle for orbital movement. Build a ship that can not only make it to the moon but sustain a 10 man crew endefintaly. Mine the moon for hydrogen 3, bring back enough to pay for the entire event. Then leap off from ther to a nea (near earth asteroid) mine that and become filthy rich. After that you will not be able to stop people from traveling through our solar system.
Reply | Report Abuse | Link to thischarwiz
not true....Earth will run out of natural resorces but mankind never will. The asteroids, are where all our resorces came from to begin with. Crashed on earth billions of years ago. The asteroids that are left out there floating in space will be the ones that Earth will someday depend on in order to servive. We have all ready landed and/or crashed into asteroids. It is cheaper in fuel cost when considering payload to get to the nearest asteroid then to take a trip to the moon and back. We as a human species must start mining asteroids and the moon (h-3) in our near future or we are headed for a dark age we may not survive.
Reply | Report Abuse | Link to thischarwiz
One payload of (h-3), about the amount that could fit into a spaceshuttle. ( I know a space shuttle is only an orbiter) could fuel the entire united states for one year. You can mine that esaly on the moon.
Reply | Report Abuse | Link to thisAlso the moon has enough water now proven recently, after we crashed a ship into it and studied the results. SO you dont have to hall water.
For radiation we could use electro magnetic feilds. Exactly like the earth does. This is being done now in labs, where they took a giant ball filled it up with melted iron and spun it to produce a magnetic field. OR we could simply coil up a bunch of copper wire, should produce a magnetic field.
Plasma thrusters, for an engine. The ship will have two rotating pods to simulate gravity.
charwiz